evanw/esbuild v0.12.8

on GitHub

Plugins can now specify sideEffects: false (#1009)

The default path resolution behavior in esbuild determines if a given file can be considered side-effect free (in the Webpack-specific sense) by reading the contents of the nearest enclosing package.json file and looking for "sideEffects": false. However, up until now this was impossible to achieve in an esbuild plugin because there was no way of returning this metadata back to esbuild.

With this release, esbuild plugins can now return sideEffects: false to mark a file as having no side effects. Here's an example:

esbuild.build({
  entryPoints: ['app.js'],
  bundle: true,
  plugins: [{
    name: 'env-plugin',
    setup(build) {
      build.onResolve({ filter: /^env$/ }, args => ({
        path: args.path,
        namespace: 'some-ns',
        sideEffects: false,
      }))
      build.onLoad({ filter: /.*/, namespace: 'some-ns' }, () => ({
        contents: `export default self.env || (self.env = getEnv())`,
      }))
    },
  }],
})

This plugin creates a virtual module that can be generated by importing the string env. However, since the plugin returns sideEffects: false, the generated virtual module will not be included in the bundle if all of the imported values from the module env end up being unused.

This feature was contributed by @chriscasola.

Remove a warning about unsupported source map comments (#1358)

This removes a warning that indicated when a source map comment couldn't be supported. Specifically, this happens when you enable source map generation and esbuild encounters a file with a source map comment pointing to an external file but doesn't have enough information to know where to look for that external file (basically when the source file doesn't have an associated directory to use for path resolution). In this case esbuild can't respect the input source map because it cannot be located. The warning was annoying so it has been removed. Source maps still won't work, however.